Method and apparatus for internal gear rolling

ABSTRACT

Apparatus including generally cylindrical dies carried on parallel axes and positioned within a bore of a workpiece. Rotation of the dies and the workpiece concurrently with axial relative movement between the circumferential surface of the dies and the bore rapidly rolls internal gear teeth in the bore without waste of workpiece material. The dies preferably are radially displaced inwardly with respect to the axis of the bore prior to being withdrawn from the bore. The method of rolling internal gear teeth includes positioning a plurality of cylindrical dies in generally parallel axial relationship within a bore of a workpiece, relatively angularly moving the exterior surface of the dies and the interior of the cylindrical opening, and relatively moving the workpiece and the dies into nesting relationship whereby the dies are disposed within the cylindrical opening in interferring engagement.

METHOD AND APPARATUS FOR INTERNAL GEAR ROLLING [75] Inventor: Elmer S. Zook, Princeton, Mass.

[73] Assignee: Reed Rolled Thread Die Company,

Holden, Mass.

[22] Filed: June 10, 1971 [21] Appl. N0.: 151,743

[52] US. Cl. ..72/91, 29/159.2, 72/100,

[51] Int. Cl. ..B2lh 5/02 [58]- Field of Search ..72/91, 94, 100, 110, 72/84, 92, 95, 108; 29/1592 [56] References Cited UNITED STATES PATENTS 3,636,744 1/1972 Motz et a1. ..72/91 1,558,086 10/1925 Gustavsen..'...

3,353,391 11/1967 Anthony 3,196,651 7/1965 Karrberg et al. ..72/91 F DRIVE MEANS 50 May 29, 1973 5 7] ABSTRACT Apparatus including generally cylindrical dies carried on parallel axes and positioned within a bore of a workpiece. Rotation of the dies and the workpiece concurrently with axial relative movement between the circumferential surface of the dies and the bore rapidly rolls internal gear teeth in the bore without waste of workpiece material. The dies preferably are radially displaced inwardly with respect to the axis of the bore prior to being withdrawn from the bore. The method of rolling internal gear teeth includes positioning a plurality of cylindrical dies in generally parallel axial relationship within a bore of a workpiece, relatively angularly moving the exterior surface of the dies and the interior of the cylindrical opening, and relatively moving the workpiece and the dies into nesting relationship whereby the dies are disposed within the cylindrical opening in interferring engagement.

11 Claims, 3 Drawing Figures 23 3/ /&

DRIVE POSITIONING MEANS MEANS l 22 l i Mb PATENImmzs m5 SHEET 2 [IF 2 INVENTOR ELMER S. ZOOK ATTORNEY METHOD AND APPARATUS FOR INTERNAL GEAR ROLLING BACKGROUND OF THE INVENTION Gear rolling has proven to be an inexpensive method of manufacturing external gears. The process produces a gear without waste material, that does not require as large a capital investment as other methods do and which uses dies capable of longlived operation. Existing methods of producing internal gears have included broaching and other cutting processes which offer none of the advantages inherent in gear rolling. In the past gear rolling has not been used to manufacture internally toothed gears despite its obvious advantages in part because of certain difficulties inclduing holding and supporting the workpiece and providing the proper flow of workpiece material to form the finished teeth. The workpiece normally used is ordinarily a relatively thin cylindrical member which resists metal flow and is vulnerable to distortion of its outer form unlike the compact solid and rigid workpiece normally used in external gear rolling.

SUMMARY OF THE INVENTION In accordance with the invention the apparatus for internal gear rolling in a workpiece member having a generally cylindrical opening therein includes a first housing carrying the workpiece member and a second housing. Means are provided for moving the housings selectively toward and away from each other. The second housing carries a plurality of generally cylindrical die members having arcuate circumferential faces with a plurality of teeth disposed thereabout. The dies are carried so that a portion of the arcuate face of each die is positioned for interferring engagement with the interior of the cylindrical opening of the workpiece when the die members are positioned within the cylindrical opening. Means are provided for mounting and relatively moving axially the first and second housing with respect to each other to position the die members within the interior of the generally cylindrical opening and in addition to rotate at least one of the members about the longitudinal axis thereof to form gear teeth about the interior of the generally cylindrical opening.

In the preferred embodiment the axes of the cylindrical opening within the workpiece and die members are parallel. The die members are three in number and a portion of each tooth is truncated. Means are provided for radially displacing the die members inwardly toward the longitudinal axis of the cylindrical opening in the workpiece member.

Also in accordance with the invention the method of forming internal gear teeth in a workpiece member having a generally cylindrical opening therein includes positioning the generally cylindrical opening in generally aligned relationship with a plurality of generally cylindrical die members carried on separate shafts and rotating at least one of the members about the longitudinal axis thereof. The workpiece member and the die members are relatively moved in a direction generally parallel to the axis of the cylindrical opening into interferring engagement with the interior of the cylindrical opening.

- Accordingly, a primary object of this invention is to provide apparatus and a method for quickly and inexpensively forming internal gears which will not produce chips as part of the manufacturing process and which will require a minimum of capital equipment investment.

Another object is to provide a method of forming internal gears which utilize tooling having a long life which will produce a product having minimum variation between successive parts.

Still another object is to provide a method and apparatus which avoids distortion of the outer surfaces of the workpiece during the forming process.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified front elevational view in partial section and to a reduced scale of apparatus embodying the present invention and showing the toothed portion of the die assembly before engagement with the workpiece;

FIG. 2 is a sectional view taken along the line 2,2 in FIG. I illustrating the means for positioning the dies radially;

FIG. 3 is an elevational view to a greatly reduced scale of a single die and its mounting in partial section showing the eccentric positioning of the die. This view has been broken away.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 there is shown apparatus inclduing a die member generally designated by the numeral 10. In the preferred embodiment there are three such dies as is most apparent in FIG. 2. Each die 10 has a generally cylindrical toothed portion 11 and shaft portions 12 which are supported by bushings 13 for rotary motion at each end. The toothed portion 11 has a raised helical tooth form disposed on a generally cylindrical portion and in addition the left end has full form relief, i.e. gradually reduced major, pitch and minor diameters for the purpose of reducing forces after the major part of the rolling operation is accomplished. The right end of toothed portion 11 is a truncated conical form, i.e. the minor diameter is unchanged from the central part of the die but the peak of each tooth is ground to produce the outer form. The die 10 must necessarily be manufactured of a hardened steel because of the loads imposed during the gear rolling operation. Each bushing 13 is preferably made of bronze or similar relatively soft bearing material and is provided with flats (not shown) on its interior transverse face to prevent relative angular motion with respect to the die. Bushings 13 are each supported by a sleeve 14 which has an exterior form which is generally cylindrical, and an eccentrically positioned aperture 14a sized for angular sliding motion with respect to bushings l3. Toothed elongated portion 14b extends from the outboard end of each sleeve. The sleeve 14 on the right-hand end of die member 10 is carried for rotary motion by a head 15.

Disposed as illustrated adjacent head 15 is a first housing member 16 of very rigid construction and adapted tofirmly grip and support a workpiece 17 which typically would be cylindrical in form. A flange 18 is fixedly secured to first housing member 16 by bolts 20 (one shown). Engaging flange 18 and first housing member 16 is a cylindrical elongated driving tube 22 which is keyed (not shown) to flange 18 to prevent relative angular motion therebetween. Drive means 23 which preferably includes an electric motor and suitable gearing or belting is coupled to driving tube 22 to provide means for rotating the workpiece 17. Carried within first housing member 16, flange 18, and cylindrical elongated driving tube 22 for both rotational and longitudinal movement is a ring gear 24 adapted for engagement with gears 14b. A bushing is provided about radial positioning tube 28 for providing an optimum bearing surface but which has been omitted in the drawing for clarity. Ring gear 24 is secured by bolts 26 (one shown) to radial positioning tube 28. At the opposite end of tube 28 a handle member is fixedly secured for angular positioning thereof. The handle is provided with vernier stop means (not shown) for accurate angular positioning. Positioning means 31 which preferably includes a hydraulicly operated piston and cylinder are connected to handle 30 and radial positioning tube 28 as well as to driving tube 22 to longitudinally move them. As will be described in more detail hereafter with maximum movement to the left the workpiece 17 will move to the left of the position illustrated such that it surrounds toothed portion 11 of die 10. With maximum movement to the right the workpiece 17 is positioned to the right of gears 14b on the right-hand sleeves 14. Accordingly, ring gear 24 does not engage gears 14b as it does in the position shown in FIG. 1. It should be understood, however, that relative longitudinal movement does occur between ring gear 24 and first housing member 16.

Disposed about the left-hand end of the dies is a second housing member 32 which is fixedly secured to a stationary member 34 of generally planar form by bolts 36 (one shown). Bolts 37 fixedly secure head to the second housing member. A bushing 38 is held by retainer 39 within stationary member 34 and second housing member 32. The bushing 38 supports a ring gear 40 which is similar to ring gear 24 disposed at the opposite end of the die members 10. A handle 42 similar to handle 30 is fixedly attached to ring gear 40 for angular positioning thereof. This handle is also provided with vernier stop means (not shown) for accurately controlling its position and an elongated member (not shown) extending radially from the portion shown in FIG. 1 for manual angular positioning thereof. Ring gear 42 engages toothed elongated portion 14c of each left-hand sleeve 14 for angular positioning thereof.

A cylindrical shaft extension 44 from die member 10 passes through aperture 14d of each left-hand sleeve 14. Attached by splines (not shown) to each extremity of the shaft extension 44 is a coupling 46, each of which has a ring 48 for connection with a drive means 50. Drive means 50 preferably includes an electric motor with suitable gears or belts or both connected by a drive shaft having universal joints at each end with one of them connecting to ring 48. The universal joints are necessary because of the radial displacement of the die members during operational procedures which will be described hereafter.

The radial positioning of the die members 10 will be most apparent by reference to FIGS. 2 and 3. Specifically referring to FIG. 3 die member 10 is shown again with its bushing 13 which is fixedly attached thereto. The bushing 13 is carried in sleeve 14 which, as is evident in this view, has the aperture 14a disposed eccen-- is further apparent by reference to FIG. 2. FIG. 2 shows the spatial relationship of the die member 10 with its tooth portion 1 1 and shaft portion 12 as well as bushing 13, sleeve 14, and ring gear 24. It should be understood, however, that the ring gear shown is in reality disposed to the opposite end of die member 10. The juxtaposition illustrated better shows the movement which occurs.

In operation first housing member 16 and ring gear 24 together with their associated structures are moved to the extreme right-hand position which as has been noted is to the right of the position illustrated. A workpiece 17 is fixed within the first housing means 16 and the vernier stop means which limit the positions of handles 30, 42 are set to a position appropriate for the maximum outward radial position desired for rolling the particular gear teeth. Next the positioning means is operated to move ring gear 24 into engagement with gears 14b of right-hand sleeves 14. The handles 30 and 42 are concurrently positioned against their stops to thereby position radially the die members 10. With the drive means turning each die member 10 the positioning means 31 then positions the workpiece 17 in nesting relationship with the toothed portion 11 of die member 10 by displacing first housing means 16, flange 18, and driving tube 22. When this has been accomplished, the gear teeth are formed on the internal diameter of the workpiece 17 and handles 30 and 42 are rotated to radially displace the die member 10 inwardly for withdrawal without distorting the rolled gear forms.

Although not shown for clarity the mechanism includes means including suitable apertures for delivering a profuse quantity of oil not only to the workpiece but also to the sleeve 14 and bushing 13 to insure proper lubrication. Filtering means (not shown) are also provided to avoid contamination of the oil supply.

In the operation of the embodiment described the workpiece 17 must be rotated during the rolling operation and the die members 10 must similarly be rotated. Power may be applied to the workpiece depending upon the particular requirements involved in forming the gears. It should be further understood that a common shaft may join drive means 23 and 50 whereby either a single electric motor is utilized or a plurality of motors are used with a shaft in between to insure absolutely synchronous movement. In one embodiment the shaft joining may include a controlled torque clutch mechanism which will selectively slip if the forces required to drive either the workpiece or the die members vary significantly.

It should be understood that the term gear teeth as used herein includes formations other than conventional gear teeth including oil grooves, splines, grooves for heat exchanging purposes and other internal forms. The formations on the die may vary accordingly to produce the desired forms. Another of the many possible variations would be to use a die with axial rather than helical teeth. The die axes although parallel to each other in the preferred embodiment may be skewed with respect to each other.

In the emboidment shown the workpiece and the dies turn during each rolling cycle although power from an electric motor may only be supplied to one which will in turn drive the other. It is necessary that two of three elements rotate to form the gears. The three elements are the die members, the die head and the workpiece. Since inherently the gear formed mates with the die members this rotation must occur even if angular drive power is only applied to one element. Other embodiments may provide for rotation of the die head with or without power applied thereto without departing from the spirit of the invention.

Thus it can be seen that the present invention provides apparatus and a method for quickly and inexpensively forming internal gears which does not produce chips as a part of the manufacturing processes, requires a minimum of capital investment, which utilizes tooling which will produce a product having a minimum variation between successive parts with a long tool life. The apparatus provided by means of a truncated die provides proper material flow and support of the workpiece avoids distortion of the outside dimensions of the workpiece during the forming process.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Apparatus for internal gear rolling in a workpiece member having a generally cylindrical opening therein comprising:

a. A first housing carrying the workpiece member;

b. A second housing;

c. A plurality of generally cylindrical die members carried by said second housing, said dies having arcuate circumferential faces with a plurality of teeth disposed thereabout, said dies being carried with the longitudinal axes radially spaced so that a portion of said arcuate face of each of said dies is positioned for interferring engagement with the interior of the cylindrical opening of the workpiece when said dies are positioned within the cylindrical opend. Means for mounting and relatively axially moving said first and second housings to position the dies within the generally cylindrical opening within the workpiece;

e. Means for rotating at least one member about the longitudinal axis thereof whereby gear teeth are formed about the interior surface of the generally cylindrical workpiece opening.

2. The apparatus as described in claim 1 wherein an axial portion of each of said die teeth is truncated whereby forces required to roll the gear teeth build up slowly during the rolling cycle.

3. The apparatus as described in claim 1 wherein said plurality of die members consists of three die members.

4. The apparatus as described in claim 1 wherein the longitudinal axis of each die and of the generally cylindrical opening within the workpiece is parallel.

5. The apparatus as described in claim 1 wherein said means for rotating at least one of said members comprises an electric motor coupled to each of the plurality of die members for driving engagement.

6. The apparatus as described in claim 1 wherein said means for rotating at least one of said members comprises an electric motor coupled to the workpiece for driving engagement thereof.

7. The apparatus as described in claim 6 further including means for selectively displacing the die members for driving engagement concurrently with the workpiece.

8. The apparatus as described in claim 1 further including means for selectively displacing the die members radially inward with respect to the longitudinal axis of the cylindrical opening in the workpiece member.

9. The apparatus as described in claim 1 wherein said first housing carrying the workpiece firmly engages and supports the outer portion thereof to prevent workpiece distortion during gear rolling.

10. The method of rolling internal gear teeth in a workpiece member having a cylindrical opening therein comprising:

a. Positioning the cylindrical opening in the workpiece member in generally aligned relationship with a plurality of generally cylindrical die members carried on separate parallel shafts;

b. Rotating at least one member about the longitudinal axis thereof whereby relative axial surface movement occurs between said die members and the workpiece member;

c. Moving the workpiece member and said die members in a direction generally parallel to the axes of the cylindrical opening into interferring engagement with the interior of the cylindrical opening.

11. The method as described in claim 10 further including moving said die members inwardly toward the axis of the generally cylindrical workpiece opening after forming of the internal gear teeth. 

1. Apparatus for internal gear rolling in a worKpiece member having a generally cylindrical opening therein comprising: a. A first housing carrying the workpiece member; b. A second housing; c. A plurality of generally cylindrical die members carried by said second housing, said dies having arcuate circumferential faces with a plurality of teeth disposed thereabout, said dies being carried with the longitudinal axes radially spaced so that a portion of said arcuate face of each of said dies is positioned for interferring engagement with the interior of the cylindrical opening of the workpiece when said dies are positioned within the cylindrical opening; d. Means for mounting and relatively axially moving said first and second housings to position the dies within the generally cylindrical opening within the workpiece; e. Means for rotating at least one member about the longitudinal axis thereof whereby gear teeth are formed about the interior surface of the generally cylindrical workpiece opening.
 2. The apparatus as described in claim 1 wherein an axial portion of each of said die teeth is truncated whereby forces required to roll the gear teeth build up slowly during the rolling cycle.
 3. The apparatus as described in claim 1 wherein said plurality of die members consists of three die members.
 4. The apparatus as described in claim 1 wherein the longitudinal axis of each die and of the generally cylindrical opening within the workpiece is parallel.
 5. The apparatus as described in claim 1 wherein said means for rotating at least one of said members comprises an electric motor coupled to each of the plurality of die members for driving engagement.
 6. The apparatus as described in claim 1 wherein said means for rotating at least one of said members comprises an electric motor coupled to the workpiece for driving engagement thereof.
 7. The apparatus as described in claim 6 further including means for selectively displacing the die members for driving engagement concurrently with the workpiece.
 8. The apparatus as described in claim 1 further including means for selectively displacing the die members radially inward with respect to the longitudinal axis of the cylindrical opening in the workpiece member.
 9. The apparatus as described in claim 1 wherein said first housing carrying the workpiece firmly engages and supports the outer portion thereof to prevent workpiece distortion during gear rolling.
 10. The method of rolling internal gear teeth in a workpiece member having a cylindrical opening therein comprising: a. Positioning the cylindrical opening in the workpiece member in generally aligned relationship with a plurality of generally cylindrical die members carried on separate parallel shafts; b. Rotating at least one member about the longitudinal axis thereof whereby relative axial surface movement occurs between said die members and the workpiece member; c. Moving the workpiece member and said die members in a direction generally parallel to the axes of the cylindrical opening into interferring engagement with the interior of the cylindrical opening.
 11. The method as described in claim 10 further including moving said die members inwardly toward the axis of the generally cylindrical workpiece opening after forming of the internal gear teeth. 